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Moulding Process

At Spectra we can offer a wide range of materials depending on the moulding process or products you choose.

Below we've sepearated these materials by moulding process, giving you an example of their uses.

Extrusion Blowmoulding is a highly versatile process, where very unique shapes, sizes and neck types can be achieved, using a variety of plastics. This versatility gives an overwhelming advantage over other bottle manufacturing processes.

Extrusion Blowmoulding is the process of manufacturing hollow plastic bottles by melting plastic resin and extruding a tube which is then clamped inside 2 halves of a water cooled mould. When the tube of molten plastic is in the mould it is then inflated using pressurised air to the shape of the mould. While inside the mould, the plastic will freeze off to the shape as it is forced against the inside of the mould. The mould will then open releasing the bottle so that the process can be repeated.

The plastics that can be used in the Extrusion Blowmoulding process include:

PE - Polyethylene

  • Polyethylene is the most common of resins that are used in blowmoulding.
  • These generally consist of HDPE (high density polyethylene) which will produce components with high stiffness, good resistance to water vapour and excellent resistance to alcohol, acids and alkali's.
  • In its natural state it will produce bottles that are opaque.
  • Various MDPE (medium density polyethylene) bottles can also be achieved which will give bottles more squeezability.
  • High gloss HDPE can be used were a very high gloss finish to the bottle is required.
  • PCR (post consumer recycled) material is now also becoming more common as it utilises recycled HDPE offering a more environmentally friendly alternative.

PP - Polypropylene

  • Polypropylene is widely used in producing bottles where an increased amount of squeezability is preferred ( when the bottle is squeezed the bottle will return to its original position).
  • Bottles blown using polypropylene will give excellent stress crack resistance, and excellent resistance to alkalis and acids.
  • In its natural state it will produce bottles with very good clarity.
  • As polypropylene has a high heat distortion it also makes it suitable for 'hot filling'.

PETG / PCTG - Polyethylene Terephthalate Glycol

  • PETG is used where very high clarity is required (comparable to a glass bottle).
  • Bottles blown using PETG will give excellent stress crack resistance.
  • PCTG is an alternative to PETG with the advantage of being able to blow more difficult shape bottles than would be achievable using PETG.

Co Extrusion

Bottles produced using the blowmoulding process can also be 'co extruded'. This process allows the bottles to be blown with the bottle wall being made up of different layers of plastics. At Spectra we utilise this process to offer our customers bottles a decorative finish that would be either unachievable or too expensive to manufacture in a single layer.

Examples of this can include:

  • HDPE inner layer with a 'Soft touch' outer layer - for a bottle that is very tactile
  • HDPE inner layer with a 'Super high gloss' outer layer - for a very high quality, gloss finish, unachievable if blown using a single material
  • PCR inner layer with coloured HDPE outer layer - for environmentally friendly bottles
  • Coloured HDPE inner layer with a different coloured HDPE outer layer - for unachievable colour effects if blown using a single colour

We are constantly reviewing this process to expand the range of Co-Extruded finishes we can offer. Please contact us to discuss any specific enquiries you may have.